1. Field
The disclosure relates to electrical discharge protection, and in particular, to electrostatic discharge (ESD) protection for amplifiers and other circuitry employing charge pumps.
2. Background
Charge pumps are commonly utilized in electronic circuitry to step a given voltage supply level up or down, and/or to invert the supply to an inverse voltage level to power a load. A charge pump may find application in, e.g., a class G amplifier architecture, wherein the supply voltages provided to an amplifier may be varied depending on the level of the input signal to be amplified. Charge pumps may also be employed to power other types of loads besides amplifiers.
To protect the terminals of a charge pump from electrostatic discharge (ESD), protection devices such as Zener diodes and RC-triggered power clamps may be coupled between terminals susceptible to ESD. Such protection devices may shunt ESD current away from the charge pump circuitry and other circuitry coupled to the terminals, thus preventing damage to such circuitry. Examples of ESD levels which a circuit may need to withstand may be as described according to, e.g., a human body model (HBM) known in the art, or the standard IEC 61000-4-2, published by the International Electrotechnical Commission. Conventional ESD protection devices may employ either on-chip or off-chip components, with off-chip components being typically more expensive than on-chip components.
During normal charge pump operation, one or more output supply voltages of the charge pump may be switched between low and high levels, depending on a gain mode selected for the charge pump. Such gain switching of the charge pump output supply voltages may inadvertently cause one or more clamps coupled to the supply voltages to turn on, undesirably leading to current leakage through the clamps. Alternatively, current drawn by a load from the charge pump may cause a large ripple to be present on the charge pump output supply voltage, also contributing to current leakage through the clamps.
It would be desirable to provide ESD protection techniques optimally compatible with charge pump operation. It would be further desirable to provide techniques for integrating such ESD protection techniques on-chip to lower their cost of implementation.